Abstract

The forming of a composite part without defects has been a challenging issue till date due to the complexity of the process. Lack of knowledge on the in- plane shear behavior of the composite during forming has always served as the prime reason for the defects. Still, a sound knowledge of diverse phenomena which make these flaws such as wrinkling, would help to optimize the performance. In addition, the possibility to form a composite part from out-of-autoclave prepreg without any defect would further enhance the process due to the cost reduction caused by eliminating the autoclave.
The work presented herein aims to investigate the intra-ply shear behavior of out- of- autoclave carbon epoxy thermoset prepreg and its effect on wrinkling using the picture frame and bias extension tests. Tests will be performed at varying temperatures and displacement rates in order to determine their contribution on deformability of the fabric. Digital image correlation was applied onto the set-up to take sequential images at various stages of deformation and capture the onset of wrinkling. Microstructural analysis was performed in order to observe the change in tow geometry throughout the shear deformation. In addition, the uni-directional and woven prepreg (8- harness and 5- harness) were compared to the scale of their deformability to determine the material which favors the forming the most. Finally, based on the response of the operating temperature (resin viscosity), displacement rate and layer counts (layer interactions) on the onset of wrinkling, an optimization method was generated using the Taguchi and Analysis of Variance technique to determine the parameter which influences, wrinkling the most.